In commerce especially as concerns mass products of daily use it is a common problem to pack product items as the above mentioned tissue paper packs to bundles of e.g. two layers of three up to five packs (i.e. six to ten packs per bundle), three layers of four up to six packs (i.e. twelve to 24 packs per bundle) or four layers of six to eight packs (i.e. 24 to 32 packs per bundle).
In some existing packaging devices, the single product items are supplied in a stream and fed into a transverse pushing mechanism, which collects e.g. four subsequent packs pushing them transversally to the incoming stream of product items. In a laterally displaced position these four collected product items fall into a receptacle. Upon this first layer of four items a second and a third layer are pushed by said transverse pushing mechanism thus grouping twelve packs in three layers of four product items in a bundle.
This type of existing packaging device, above, may suffer from several disadvantages. First, during the transversal, pushing of the group of product items the infeed process to the transverse pushing mechanism may be interrupted. For example, only after the group of product items has fallen into the receptacle the next group of items can be supplied to the transverse mechanism. This is a first limit to the overall handling capacity of this packaging device.
A second problem is the fact that the product items from the transverse pushing mechanism fall into a receptacle. This means that during a certain period of the packaging action the products are merely under the influence of gravity. The handling speed and acceleration of the product items is naturally bounded under the influence of gravity. Finally, the product items just fall into the receptacle, thus control may be lacking for the product items, and makes the process vulnerable to disturbances and even breakdowns of the packaging device.
In the field of packaging techniques, other references relate to the grouping, stacking, layering etc. of product items. For example U.S. Pat. No. 6,164,045 discloses a device for packaging groups, i.e. layers, of packages in a carton or the like, wherein product items individually arriving in a supply stream are collected in an area of the grouping station so as to form rows of packages. The latter may be again pushed off in the transverse direction by a transverse slide onto a collecting plate in order to establish layers comprising a plurality of rows of packages. The complete layers are handled by a lifting conveyor and delivered to a carton.
Aforesaid device for packaging groups may suffer from some of the same disadvantage as discussed above, namely that during the transverse stroke of the transverse slide no new product items can be loaded into the transverse slide thus limiting the capacity of the device.
Further, EP 0 061 631 A1 and U.S. Pat. No. 2,825,475 refer to the problem of layering flat products, like rigid, semi-rigid or flexible sheet-like elements, for example paper handkerchiefs. Both publications disclose elevator means comprising two counter-rotating crawler-like tracks each provided with support elements onto which successively sheet-like elements coming from a feeding group can be discarded. Thus on each pair of support elements on the crawler-like tracks a stack of sheet-like elements may be formed.